Condensation in the extension pitched roof loft

[Skysky69]

I know this must have been covered to death, but wondered if anyone had any ideas. We have recently had a 3 metre extension across the back of our 1960s semi detached house. It has a pitched tiled roof with two velux windows in and vents at the bottom of the roof behind and just above the guttering.

The builder is at a loss to explain why we are experiencing bad condensation that is dripping through on the newly plastered ceiling in a patch where the roof meets the wall

They came back the other week and cut the felt back as they were worried the felt was covering the vents slightly and therefore would restrict air flow. He has been back today and has put his hand inside and it is still soaking. He said it is under the felt therefore it cannot be a leak and must be sweating and condensation. He has said about maybe inserting some ventilation tiles higher up the roof but has said he is not sure why it is condensating so badly as there is lots of ventilation currently in place.

Any ideas?

 

[noseall]

Fairly normal for a Winter build to get a bit 'sweaty' whilst the building is drying out.

Hardly surprising considering all the rain we have had.

 

[JohnD]

try this:

//www.diynot.com/forums/viewtopic.php?t=160032

 

[tony1851]

@skysky, what insulation did you use (type? thickness? position within the roof?).
Was a vapour barrier incorporated?

 

[Skysky69]

Fairly normal for a Winter build to get a bit 'sweaty' whilst the building is drying out.

Hardly surprising considering all the rain we have had.

The build and plastering etc. was finished at the beginning of December - is it usual to take this long to dry out?

 

[Skysky69]

Thanks for your help - the insulation was boards that went in between the joints. On top of the boards went the felt and then on top of the felt the batoning and then the tiles.

The insulation had silver stuff on top if that is any help lol! and I think the roof plaster boards could have been pink on one side? Apparently the wetness is under the felt, but above the insulation boards.

At the moment the wetness seems to be running down the insides and then dripping onto the new plaster where the roof meets the wall. I don't want to paint over it as I am not sure whether it will still be there but I just can't see it if it is decorated?

I think the roof pitch is about 15/16 degrees, should I have ventilation of some form at the top of the tiles where they meet the wall as well as the bottom by the guttering?

 

[shane12345]

What tiles are on it? Sounds to me like it's leaking.

I'd guess its blowing under the tiles and coming through the lath nails.

 

[shane12345]

Some pictures would be a bonus please.

 

[Skysky69]

I will take some when I get back and post them.

Would the moisture be above or below the felt if it was leaking?

 

[shane12345]

It could end up on both sides really. Double check there's none on top of the felt yourself.